M20 dyno results (knock limited)

[zaq123]

Just dyno'd this 2.9L 10:1 with Schrick 284/272, ITBs and completely original AMC head with Supertech valves and OEM springs/rockers. This engine is knock limited for whatever reason on 93 octane (98 ron).
Timing table is the max it wanted to handle without knock. I know AMC head isn't ideal. But my freshly rebuilt 885 had a crack and I just wanted to enjoy this car already hence was like F' IT and bolted AMC head to it. Have new 885 and maybe will drop it off to be machined and bolt it over the winter.
What's your thoughts on this timing and dyno?

[digger]

I’d be looking at the cam timing with adjustable cam gear as a couple of members either here or old e30tech forum found a bunch retarding the cam . The cylinder head is definitely not ideal and likely restricting things somewhat.

[DesertBMW]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

[zaq123]

I’d be looking at the cam timing with adjustable cam gear as a couple of members either here or old e30tech forum found a bunch retarding the cam . The cylinder head is definitely not ideal and likely restricting things somewhat.

cam was set to Schrik Spec with adj. cam gear, 4deg. retarded.

[zaq123]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

M52B28 is 193HP. This Dyno is more on par with N52B30, 231HP (196WHP with ~15% loss for the drivetrain). 60HP gain from stock M20B25( about 35% jump) is not exactly WAR chip kind of mod.

[AWDBOB]

This is too funny- I've known KP since like 2008 lol. He sent me a pic of your car on the dyno!

Jak Stoll in Louisville had issues with his AMC head. The chambers were smaller than a genuine 885 and they varied by up to 4cc due to poor machining.

Cinnabar325is owns Mission Motorwerks in Bechtelsville and might be able to get the head right

[88Sedan]

Results are not bad. I wonder if there would be more area under the curve w/slightly less duration on the cam. With the amc head on it might be more optimized since max head flow would be less than an 885. 200 whp sounds fun though.

[MrBurgundy]

first why even waste all that time and money on M20 just to have the same power as bone stock M52B28? It is well known that M20 has poor chamber design, that is why the engine stock comes with 9.3:1 compression ratio, and then even with that it will knock on hot day.
If your project is limited with knock with 93 octane. I would try some 117vp racing fuel, just to see what can your engine do with that.

lol people who come in just shit on other people are truly insufferable.

first, this m20 is making more horsepower than a stock m52.

secondly, m20s sound way better

third, its the original or at least, period correct motor.

24v swapped cars are played out and nothing exciting, especially a m52 swap.

an almost 200whp m20 is fucking cool.

[digger]

cam was set to Schrik Spec with adj. cam gear, 4deg. retarded.

the power numbers are pretty good.

If you are confident the cam is dialed in to spec then it’s likely the head that’s holding you back a bit. The un modified amc is rough on the chamber and ports. I seem to recall it flows like 15cfm less than the 885 bmw casting and the shape is rubbish but I don’t know where I saw that. I haven’t cc the stock amc but as above the variation in cc seems plausible

What was piston to head clearance ?